linux/arch/x86/kernel/hpet.c
Paul E. McKenney efc8b329c7 clocksource: Verify HPET and PMTMR when TSC unverified
On systems with two or fewer sockets, when the boot CPU has CONSTANT_TSC,
NONSTOP_TSC, and TSC_ADJUST, clocksource watchdog verification of the
TSC is disabled.  This works well much of the time, but there is the
occasional production-level system that meets all of these criteria, but
which still has a TSC that skews significantly from atomic-clock time.
This is usually attributed to a firmware or hardware fault.  Yes, the
various NTP daemons do express their opinions of userspace-to-atomic-clock
time skew, but they put them in various places, depending on the daemon
and distro in question.  It would therefore be good for the kernel to
have some clue that there is a problem.

The old behavior of marking the TSC unstable is a non-starter because a
great many workloads simply cannot tolerate the overheads and latencies
of the various non-TSC clocksources.  In addition, NTP-corrected systems
sometimes can tolerate significant kernel-space time skew as long as
the userspace time sources are within epsilon of atomic-clock time.

Therefore, when watchdog verification of TSC is disabled, enable it for
HPET and PMTMR (AKA ACPI PM timer).  This provides the needed in-kernel
time-skew diagnostic without degrading the system's performance.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Waiman Long <longman@redhat.com>
Cc: <x86@kernel.org>
Tested-by: Feng Tang <feng.tang@intel.com>
2023-02-02 14:23:02 -08:00

1474 lines
36 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/export.h>
#include <linux/delay.h>
#include <linux/hpet.h>
#include <linux/cpu.h>
#include <linux/irq.h>
#include <asm/irq_remapping.h>
#include <asm/hpet.h>
#include <asm/time.h>
#include <asm/mwait.h>
#undef pr_fmt
#define pr_fmt(fmt) "hpet: " fmt
enum hpet_mode {
HPET_MODE_UNUSED,
HPET_MODE_LEGACY,
HPET_MODE_CLOCKEVT,
HPET_MODE_DEVICE,
};
struct hpet_channel {
struct clock_event_device evt;
unsigned int num;
unsigned int cpu;
unsigned int irq;
unsigned int in_use;
enum hpet_mode mode;
unsigned int boot_cfg;
char name[10];
};
struct hpet_base {
unsigned int nr_channels;
unsigned int nr_clockevents;
unsigned int boot_cfg;
struct hpet_channel *channels;
};
#define HPET_MASK CLOCKSOURCE_MASK(32)
#define HPET_MIN_CYCLES 128
#define HPET_MIN_PROG_DELTA (HPET_MIN_CYCLES + (HPET_MIN_CYCLES >> 1))
/*
* HPET address is set in acpi/boot.c, when an ACPI entry exists
*/
unsigned long hpet_address;
u8 hpet_blockid; /* OS timer block num */
bool hpet_msi_disable;
#ifdef CONFIG_GENERIC_MSI_IRQ
static DEFINE_PER_CPU(struct hpet_channel *, cpu_hpet_channel);
static struct irq_domain *hpet_domain;
#endif
static void __iomem *hpet_virt_address;
static struct hpet_base hpet_base;
static bool hpet_legacy_int_enabled;
static unsigned long hpet_freq;
bool boot_hpet_disable;
bool hpet_force_user;
static bool hpet_verbose;
static inline
struct hpet_channel *clockevent_to_channel(struct clock_event_device *evt)
{
return container_of(evt, struct hpet_channel, evt);
}
inline unsigned int hpet_readl(unsigned int a)
{
return readl(hpet_virt_address + a);
}
static inline void hpet_writel(unsigned int d, unsigned int a)
{
writel(d, hpet_virt_address + a);
}
static inline void hpet_set_mapping(void)
{
hpet_virt_address = ioremap(hpet_address, HPET_MMAP_SIZE);
}
static inline void hpet_clear_mapping(void)
{
iounmap(hpet_virt_address);
hpet_virt_address = NULL;
}
/*
* HPET command line enable / disable
*/
static int __init hpet_setup(char *str)
{
while (str) {
char *next = strchr(str, ',');
if (next)
*next++ = 0;
if (!strncmp("disable", str, 7))
boot_hpet_disable = true;
if (!strncmp("force", str, 5))
hpet_force_user = true;
if (!strncmp("verbose", str, 7))
hpet_verbose = true;
str = next;
}
return 1;
}
__setup("hpet=", hpet_setup);
static int __init disable_hpet(char *str)
{
boot_hpet_disable = true;
return 1;
}
__setup("nohpet", disable_hpet);
static inline int is_hpet_capable(void)
{
return !boot_hpet_disable && hpet_address;
}
/**
* is_hpet_enabled - Check whether the legacy HPET timer interrupt is enabled
*/
int is_hpet_enabled(void)
{
return is_hpet_capable() && hpet_legacy_int_enabled;
}
EXPORT_SYMBOL_GPL(is_hpet_enabled);
static void _hpet_print_config(const char *function, int line)
{
u32 i, id, period, cfg, status, channels, l, h;
pr_info("%s(%d):\n", function, line);
id = hpet_readl(HPET_ID);
period = hpet_readl(HPET_PERIOD);
pr_info("ID: 0x%x, PERIOD: 0x%x\n", id, period);
cfg = hpet_readl(HPET_CFG);
status = hpet_readl(HPET_STATUS);
pr_info("CFG: 0x%x, STATUS: 0x%x\n", cfg, status);
l = hpet_readl(HPET_COUNTER);
h = hpet_readl(HPET_COUNTER+4);
pr_info("COUNTER_l: 0x%x, COUNTER_h: 0x%x\n", l, h);
channels = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT) + 1;
for (i = 0; i < channels; i++) {
l = hpet_readl(HPET_Tn_CFG(i));
h = hpet_readl(HPET_Tn_CFG(i)+4);
pr_info("T%d: CFG_l: 0x%x, CFG_h: 0x%x\n", i, l, h);
l = hpet_readl(HPET_Tn_CMP(i));
h = hpet_readl(HPET_Tn_CMP(i)+4);
pr_info("T%d: CMP_l: 0x%x, CMP_h: 0x%x\n", i, l, h);
l = hpet_readl(HPET_Tn_ROUTE(i));
h = hpet_readl(HPET_Tn_ROUTE(i)+4);
pr_info("T%d ROUTE_l: 0x%x, ROUTE_h: 0x%x\n", i, l, h);
}
}
#define hpet_print_config() \
do { \
if (hpet_verbose) \
_hpet_print_config(__func__, __LINE__); \
} while (0)
/*
* When the HPET driver (/dev/hpet) is enabled, we need to reserve
* timer 0 and timer 1 in case of RTC emulation.
*/
#ifdef CONFIG_HPET
static void __init hpet_reserve_platform_timers(void)
{
struct hpet_data hd;
unsigned int i;
memset(&hd, 0, sizeof(hd));
hd.hd_phys_address = hpet_address;
hd.hd_address = hpet_virt_address;
hd.hd_nirqs = hpet_base.nr_channels;
/*
* NOTE that hd_irq[] reflects IOAPIC input pins (LEGACY_8254
* is wrong for i8259!) not the output IRQ. Many BIOS writers
* don't bother configuring *any* comparator interrupts.
*/
hd.hd_irq[0] = HPET_LEGACY_8254;
hd.hd_irq[1] = HPET_LEGACY_RTC;
for (i = 0; i < hpet_base.nr_channels; i++) {
struct hpet_channel *hc = hpet_base.channels + i;
if (i >= 2)
hd.hd_irq[i] = hc->irq;
switch (hc->mode) {
case HPET_MODE_UNUSED:
case HPET_MODE_DEVICE:
hc->mode = HPET_MODE_DEVICE;
break;
case HPET_MODE_CLOCKEVT:
case HPET_MODE_LEGACY:
hpet_reserve_timer(&hd, hc->num);
break;
}
}
hpet_alloc(&hd);
}
static void __init hpet_select_device_channel(void)
{
int i;
for (i = 0; i < hpet_base.nr_channels; i++) {
struct hpet_channel *hc = hpet_base.channels + i;
/* Associate the first unused channel to /dev/hpet */
if (hc->mode == HPET_MODE_UNUSED) {
hc->mode = HPET_MODE_DEVICE;
return;
}
}
}
#else
static inline void hpet_reserve_platform_timers(void) { }
static inline void hpet_select_device_channel(void) {}
#endif
/* Common HPET functions */
static void hpet_stop_counter(void)
{
u32 cfg = hpet_readl(HPET_CFG);
cfg &= ~HPET_CFG_ENABLE;
hpet_writel(cfg, HPET_CFG);
}
static void hpet_reset_counter(void)
{
hpet_writel(0, HPET_COUNTER);
hpet_writel(0, HPET_COUNTER + 4);
}
static void hpet_start_counter(void)
{
unsigned int cfg = hpet_readl(HPET_CFG);
cfg |= HPET_CFG_ENABLE;
hpet_writel(cfg, HPET_CFG);
}
static void hpet_restart_counter(void)
{
hpet_stop_counter();
hpet_reset_counter();
hpet_start_counter();
}
static void hpet_resume_device(void)
{
force_hpet_resume();
}
static void hpet_resume_counter(struct clocksource *cs)
{
hpet_resume_device();
hpet_restart_counter();
}
static void hpet_enable_legacy_int(void)
{
unsigned int cfg = hpet_readl(HPET_CFG);
cfg |= HPET_CFG_LEGACY;
hpet_writel(cfg, HPET_CFG);
hpet_legacy_int_enabled = true;
}
static int hpet_clkevt_set_state_periodic(struct clock_event_device *evt)
{
unsigned int channel = clockevent_to_channel(evt)->num;
unsigned int cfg, cmp, now;
uint64_t delta;
hpet_stop_counter();
delta = ((uint64_t)(NSEC_PER_SEC / HZ)) * evt->mult;
delta >>= evt->shift;
now = hpet_readl(HPET_COUNTER);
cmp = now + (unsigned int)delta;
cfg = hpet_readl(HPET_Tn_CFG(channel));
cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | HPET_TN_SETVAL |
HPET_TN_32BIT;
hpet_writel(cfg, HPET_Tn_CFG(channel));
hpet_writel(cmp, HPET_Tn_CMP(channel));
udelay(1);
/*
* HPET on AMD 81xx needs a second write (with HPET_TN_SETVAL
* cleared) to T0_CMP to set the period. The HPET_TN_SETVAL
* bit is automatically cleared after the first write.
* (See AMD-8111 HyperTransport I/O Hub Data Sheet,
* Publication # 24674)
*/
hpet_writel((unsigned int)delta, HPET_Tn_CMP(channel));
hpet_start_counter();
hpet_print_config();
return 0;
}
static int hpet_clkevt_set_state_oneshot(struct clock_event_device *evt)
{
unsigned int channel = clockevent_to_channel(evt)->num;
unsigned int cfg;
cfg = hpet_readl(HPET_Tn_CFG(channel));
cfg &= ~HPET_TN_PERIODIC;
cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
hpet_writel(cfg, HPET_Tn_CFG(channel));
return 0;
}
static int hpet_clkevt_set_state_shutdown(struct clock_event_device *evt)
{
unsigned int channel = clockevent_to_channel(evt)->num;
unsigned int cfg;
cfg = hpet_readl(HPET_Tn_CFG(channel));
cfg &= ~HPET_TN_ENABLE;
hpet_writel(cfg, HPET_Tn_CFG(channel));
return 0;
}
static int hpet_clkevt_legacy_resume(struct clock_event_device *evt)
{
hpet_enable_legacy_int();
hpet_print_config();
return 0;
}
static int
hpet_clkevt_set_next_event(unsigned long delta, struct clock_event_device *evt)
{
unsigned int channel = clockevent_to_channel(evt)->num;
u32 cnt;
s32 res;
cnt = hpet_readl(HPET_COUNTER);
cnt += (u32) delta;
hpet_writel(cnt, HPET_Tn_CMP(channel));
/*
* HPETs are a complete disaster. The compare register is
* based on a equal comparison and neither provides a less
* than or equal functionality (which would require to take
* the wraparound into account) nor a simple count down event
* mode. Further the write to the comparator register is
* delayed internally up to two HPET clock cycles in certain
* chipsets (ATI, ICH9,10). Some newer AMD chipsets have even
* longer delays. We worked around that by reading back the
* compare register, but that required another workaround for
* ICH9,10 chips where the first readout after write can
* return the old stale value. We already had a minimum
* programming delta of 5us enforced, but a NMI or SMI hitting
* between the counter readout and the comparator write can
* move us behind that point easily. Now instead of reading
* the compare register back several times, we make the ETIME
* decision based on the following: Return ETIME if the
* counter value after the write is less than HPET_MIN_CYCLES
* away from the event or if the counter is already ahead of
* the event. The minimum programming delta for the generic
* clockevents code is set to 1.5 * HPET_MIN_CYCLES.
*/
res = (s32)(cnt - hpet_readl(HPET_COUNTER));
return res < HPET_MIN_CYCLES ? -ETIME : 0;
}
static void hpet_init_clockevent(struct hpet_channel *hc, unsigned int rating)
{
struct clock_event_device *evt = &hc->evt;
evt->rating = rating;
evt->irq = hc->irq;
evt->name = hc->name;
evt->cpumask = cpumask_of(hc->cpu);
evt->set_state_oneshot = hpet_clkevt_set_state_oneshot;
evt->set_next_event = hpet_clkevt_set_next_event;
evt->set_state_shutdown = hpet_clkevt_set_state_shutdown;
evt->features = CLOCK_EVT_FEAT_ONESHOT;
if (hc->boot_cfg & HPET_TN_PERIODIC) {
evt->features |= CLOCK_EVT_FEAT_PERIODIC;
evt->set_state_periodic = hpet_clkevt_set_state_periodic;
}
}
static void __init hpet_legacy_clockevent_register(struct hpet_channel *hc)
{
/*
* Start HPET with the boot CPU's cpumask and make it global after
* the IO_APIC has been initialized.
*/
hc->cpu = boot_cpu_data.cpu_index;
strncpy(hc->name, "hpet", sizeof(hc->name));
hpet_init_clockevent(hc, 50);
hc->evt.tick_resume = hpet_clkevt_legacy_resume;
/*
* Legacy horrors and sins from the past. HPET used periodic mode
* unconditionally forever on the legacy channel 0. Removing the
* below hack and using the conditional in hpet_init_clockevent()
* makes at least Qemu and one hardware machine fail to boot.
* There are two issues which cause the boot failure:
*
* #1 After the timer delivery test in IOAPIC and the IOAPIC setup
* the next interrupt is not delivered despite the HPET channel
* being programmed correctly. Reprogramming the HPET after
* switching to IOAPIC makes it work again. After fixing this,
* the next issue surfaces:
*
* #2 Due to the unconditional periodic mode availability the Local
* APIC timer calibration can hijack the global clockevents
* event handler without causing damage. Using oneshot at this
* stage makes if hang because the HPET does not get
* reprogrammed due to the handler hijacking. Duh, stupid me!
*
* Both issues require major surgery and especially the kick HPET
* again after enabling IOAPIC results in really nasty hackery.
* This 'assume periodic works' magic has survived since HPET
* support got added, so it's questionable whether this should be
* fixed. Both Qemu and the failing hardware machine support
* periodic mode despite the fact that both don't advertise it in
* the configuration register and both need that extra kick after
* switching to IOAPIC. Seems to be a feature...
*/
hc->evt.features |= CLOCK_EVT_FEAT_PERIODIC;
hc->evt.set_state_periodic = hpet_clkevt_set_state_periodic;
/* Start HPET legacy interrupts */
hpet_enable_legacy_int();
clockevents_config_and_register(&hc->evt, hpet_freq,
HPET_MIN_PROG_DELTA, 0x7FFFFFFF);
global_clock_event = &hc->evt;
pr_debug("Clockevent registered\n");
}
/*
* HPET MSI Support
*/
#ifdef CONFIG_GENERIC_MSI_IRQ
static void hpet_msi_unmask(struct irq_data *data)
{
struct hpet_channel *hc = irq_data_get_irq_handler_data(data);
unsigned int cfg;
cfg = hpet_readl(HPET_Tn_CFG(hc->num));
cfg |= HPET_TN_ENABLE | HPET_TN_FSB;
hpet_writel(cfg, HPET_Tn_CFG(hc->num));
}
static void hpet_msi_mask(struct irq_data *data)
{
struct hpet_channel *hc = irq_data_get_irq_handler_data(data);
unsigned int cfg;
cfg = hpet_readl(HPET_Tn_CFG(hc->num));
cfg &= ~(HPET_TN_ENABLE | HPET_TN_FSB);
hpet_writel(cfg, HPET_Tn_CFG(hc->num));
}
static void hpet_msi_write(struct hpet_channel *hc, struct msi_msg *msg)
{
hpet_writel(msg->data, HPET_Tn_ROUTE(hc->num));
hpet_writel(msg->address_lo, HPET_Tn_ROUTE(hc->num) + 4);
}
static void hpet_msi_write_msg(struct irq_data *data, struct msi_msg *msg)
{
hpet_msi_write(irq_data_get_irq_handler_data(data), msg);
}
static struct irq_chip hpet_msi_controller __ro_after_init = {
.name = "HPET-MSI",
.irq_unmask = hpet_msi_unmask,
.irq_mask = hpet_msi_mask,
.irq_ack = irq_chip_ack_parent,
.irq_set_affinity = msi_domain_set_affinity,
.irq_retrigger = irq_chip_retrigger_hierarchy,
.irq_write_msi_msg = hpet_msi_write_msg,
.flags = IRQCHIP_SKIP_SET_WAKE | IRQCHIP_AFFINITY_PRE_STARTUP,
};
static int hpet_msi_init(struct irq_domain *domain,
struct msi_domain_info *info, unsigned int virq,
irq_hw_number_t hwirq, msi_alloc_info_t *arg)
{
irq_set_status_flags(virq, IRQ_MOVE_PCNTXT);
irq_domain_set_info(domain, virq, arg->hwirq, info->chip, NULL,
handle_edge_irq, arg->data, "edge");
return 0;
}
static void hpet_msi_free(struct irq_domain *domain,
struct msi_domain_info *info, unsigned int virq)
{
irq_clear_status_flags(virq, IRQ_MOVE_PCNTXT);
}
static struct msi_domain_ops hpet_msi_domain_ops = {
.msi_init = hpet_msi_init,
.msi_free = hpet_msi_free,
};
static struct msi_domain_info hpet_msi_domain_info = {
.ops = &hpet_msi_domain_ops,
.chip = &hpet_msi_controller,
.flags = MSI_FLAG_USE_DEF_DOM_OPS,
};
static struct irq_domain *hpet_create_irq_domain(int hpet_id)
{
struct msi_domain_info *domain_info;
struct irq_domain *parent, *d;
struct fwnode_handle *fn;
struct irq_fwspec fwspec;
if (x86_vector_domain == NULL)
return NULL;
domain_info = kzalloc(sizeof(*domain_info), GFP_KERNEL);
if (!domain_info)
return NULL;
*domain_info = hpet_msi_domain_info;
domain_info->data = (void *)(long)hpet_id;
fn = irq_domain_alloc_named_id_fwnode(hpet_msi_controller.name,
hpet_id);
if (!fn) {
kfree(domain_info);
return NULL;
}
fwspec.fwnode = fn;
fwspec.param_count = 1;
fwspec.param[0] = hpet_id;
parent = irq_find_matching_fwspec(&fwspec, DOMAIN_BUS_ANY);
if (!parent) {
irq_domain_free_fwnode(fn);
kfree(domain_info);
return NULL;
}
if (parent != x86_vector_domain)
hpet_msi_controller.name = "IR-HPET-MSI";
d = msi_create_irq_domain(fn, domain_info, parent);
if (!d) {
irq_domain_free_fwnode(fn);
kfree(domain_info);
}
return d;
}
static inline int hpet_dev_id(struct irq_domain *domain)
{
struct msi_domain_info *info = msi_get_domain_info(domain);
return (int)(long)info->data;
}
static int hpet_assign_irq(struct irq_domain *domain, struct hpet_channel *hc,
int dev_num)
{
struct irq_alloc_info info;
init_irq_alloc_info(&info, NULL);
info.type = X86_IRQ_ALLOC_TYPE_HPET;
info.data = hc;
info.devid = hpet_dev_id(domain);
info.hwirq = dev_num;
return irq_domain_alloc_irqs(domain, 1, NUMA_NO_NODE, &info);
}
static int hpet_clkevt_msi_resume(struct clock_event_device *evt)
{
struct hpet_channel *hc = clockevent_to_channel(evt);
struct irq_data *data = irq_get_irq_data(hc->irq);
struct msi_msg msg;
/* Restore the MSI msg and unmask the interrupt */
irq_chip_compose_msi_msg(data, &msg);
hpet_msi_write(hc, &msg);
hpet_msi_unmask(data);
return 0;
}
static irqreturn_t hpet_msi_interrupt_handler(int irq, void *data)
{
struct hpet_channel *hc = data;
struct clock_event_device *evt = &hc->evt;
if (!evt->event_handler) {
pr_info("Spurious interrupt HPET channel %d\n", hc->num);
return IRQ_HANDLED;
}
evt->event_handler(evt);
return IRQ_HANDLED;
}
static int hpet_setup_msi_irq(struct hpet_channel *hc)
{
if (request_irq(hc->irq, hpet_msi_interrupt_handler,
IRQF_TIMER | IRQF_NOBALANCING,
hc->name, hc))
return -1;
disable_irq(hc->irq);
irq_set_affinity(hc->irq, cpumask_of(hc->cpu));
enable_irq(hc->irq);
pr_debug("%s irq %u for MSI\n", hc->name, hc->irq);
return 0;
}
/* Invoked from the hotplug callback on @cpu */
static void init_one_hpet_msi_clockevent(struct hpet_channel *hc, int cpu)
{
struct clock_event_device *evt = &hc->evt;
hc->cpu = cpu;
per_cpu(cpu_hpet_channel, cpu) = hc;
hpet_setup_msi_irq(hc);
hpet_init_clockevent(hc, 110);
evt->tick_resume = hpet_clkevt_msi_resume;
clockevents_config_and_register(evt, hpet_freq, HPET_MIN_PROG_DELTA,
0x7FFFFFFF);
}
static struct hpet_channel *hpet_get_unused_clockevent(void)
{
int i;
for (i = 0; i < hpet_base.nr_channels; i++) {
struct hpet_channel *hc = hpet_base.channels + i;
if (hc->mode != HPET_MODE_CLOCKEVT || hc->in_use)
continue;
hc->in_use = 1;
return hc;
}
return NULL;
}
static int hpet_cpuhp_online(unsigned int cpu)
{
struct hpet_channel *hc = hpet_get_unused_clockevent();
if (hc)
init_one_hpet_msi_clockevent(hc, cpu);
return 0;
}
static int hpet_cpuhp_dead(unsigned int cpu)
{
struct hpet_channel *hc = per_cpu(cpu_hpet_channel, cpu);
if (!hc)
return 0;
free_irq(hc->irq, hc);
hc->in_use = 0;
per_cpu(cpu_hpet_channel, cpu) = NULL;
return 0;
}
static void __init hpet_select_clockevents(void)
{
unsigned int i;
hpet_base.nr_clockevents = 0;
/* No point if MSI is disabled or CPU has an Always Runing APIC Timer */
if (hpet_msi_disable || boot_cpu_has(X86_FEATURE_ARAT))
return;
hpet_print_config();
hpet_domain = hpet_create_irq_domain(hpet_blockid);
if (!hpet_domain)
return;
for (i = 0; i < hpet_base.nr_channels; i++) {
struct hpet_channel *hc = hpet_base.channels + i;
int irq;
if (hc->mode != HPET_MODE_UNUSED)
continue;
/* Only consider HPET channel with MSI support */
if (!(hc->boot_cfg & HPET_TN_FSB_CAP))
continue;
sprintf(hc->name, "hpet%d", i);
irq = hpet_assign_irq(hpet_domain, hc, hc->num);
if (irq <= 0)
continue;
hc->irq = irq;
hc->mode = HPET_MODE_CLOCKEVT;
if (++hpet_base.nr_clockevents == num_possible_cpus())
break;
}
pr_info("%d channels of %d reserved for per-cpu timers\n",
hpet_base.nr_channels, hpet_base.nr_clockevents);
}
#else
static inline void hpet_select_clockevents(void) { }
#define hpet_cpuhp_online NULL
#define hpet_cpuhp_dead NULL
#endif
/*
* Clock source related code
*/
#if defined(CONFIG_SMP) && defined(CONFIG_64BIT)
/*
* Reading the HPET counter is a very slow operation. If a large number of
* CPUs are trying to access the HPET counter simultaneously, it can cause
* massive delays and slow down system performance dramatically. This may
* happen when HPET is the default clock source instead of TSC. For a
* really large system with hundreds of CPUs, the slowdown may be so
* severe, that it can actually crash the system because of a NMI watchdog
* soft lockup, for example.
*
* If multiple CPUs are trying to access the HPET counter at the same time,
* we don't actually need to read the counter multiple times. Instead, the
* other CPUs can use the counter value read by the first CPU in the group.
*
* This special feature is only enabled on x86-64 systems. It is unlikely
* that 32-bit x86 systems will have enough CPUs to require this feature
* with its associated locking overhead. We also need 64-bit atomic read.
*
* The lock and the HPET value are stored together and can be read in a
* single atomic 64-bit read. It is explicitly assumed that arch_spinlock_t
* is 32 bits in size.
*/
union hpet_lock {
struct {
arch_spinlock_t lock;
u32 value;
};
u64 lockval;
};
static union hpet_lock hpet __cacheline_aligned = {
{ .lock = __ARCH_SPIN_LOCK_UNLOCKED, },
};
static u64 read_hpet(struct clocksource *cs)
{
unsigned long flags;
union hpet_lock old, new;
BUILD_BUG_ON(sizeof(union hpet_lock) != 8);
/*
* Read HPET directly if in NMI.
*/
if (in_nmi())
return (u64)hpet_readl(HPET_COUNTER);
/*
* Read the current state of the lock and HPET value atomically.
*/
old.lockval = READ_ONCE(hpet.lockval);
if (arch_spin_is_locked(&old.lock))
goto contended;
local_irq_save(flags);
if (arch_spin_trylock(&hpet.lock)) {
new.value = hpet_readl(HPET_COUNTER);
/*
* Use WRITE_ONCE() to prevent store tearing.
*/
WRITE_ONCE(hpet.value, new.value);
arch_spin_unlock(&hpet.lock);
local_irq_restore(flags);
return (u64)new.value;
}
local_irq_restore(flags);
contended:
/*
* Contended case
* --------------
* Wait until the HPET value change or the lock is free to indicate
* its value is up-to-date.
*
* It is possible that old.value has already contained the latest
* HPET value while the lock holder was in the process of releasing
* the lock. Checking for lock state change will enable us to return
* the value immediately instead of waiting for the next HPET reader
* to come along.
*/
do {
cpu_relax();
new.lockval = READ_ONCE(hpet.lockval);
} while ((new.value == old.value) && arch_spin_is_locked(&new.lock));
return (u64)new.value;
}
#else
/*
* For UP or 32-bit.
*/
static u64 read_hpet(struct clocksource *cs)
{
return (u64)hpet_readl(HPET_COUNTER);
}
#endif
static struct clocksource clocksource_hpet = {
.name = "hpet",
.rating = 250,
.read = read_hpet,
.mask = HPET_MASK,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
.resume = hpet_resume_counter,
};
/*
* AMD SB700 based systems with spread spectrum enabled use a SMM based
* HPET emulation to provide proper frequency setting.
*
* On such systems the SMM code is initialized with the first HPET register
* access and takes some time to complete. During this time the config
* register reads 0xffffffff. We check for max 1000 loops whether the
* config register reads a non-0xffffffff value to make sure that the
* HPET is up and running before we proceed any further.
*
* A counting loop is safe, as the HPET access takes thousands of CPU cycles.
*
* On non-SB700 based machines this check is only done once and has no
* side effects.
*/
static bool __init hpet_cfg_working(void)
{
int i;
for (i = 0; i < 1000; i++) {
if (hpet_readl(HPET_CFG) != 0xFFFFFFFF)
return true;
}
pr_warn("Config register invalid. Disabling HPET\n");
return false;
}
static bool __init hpet_counting(void)
{
u64 start, now, t1;
hpet_restart_counter();
t1 = hpet_readl(HPET_COUNTER);
start = rdtsc();
/*
* We don't know the TSC frequency yet, but waiting for
* 200000 TSC cycles is safe:
* 4 GHz == 50us
* 1 GHz == 200us
*/
do {
if (t1 != hpet_readl(HPET_COUNTER))
return true;
now = rdtsc();
} while ((now - start) < 200000UL);
pr_warn("Counter not counting. HPET disabled\n");
return false;
}
static bool __init mwait_pc10_supported(void)
{
unsigned int eax, ebx, ecx, mwait_substates;
if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
return false;
if (!cpu_feature_enabled(X86_FEATURE_MWAIT))
return false;
if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
return false;
cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &mwait_substates);
return (ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) &&
(ecx & CPUID5_ECX_INTERRUPT_BREAK) &&
(mwait_substates & (0xF << 28));
}
/*
* Check whether the system supports PC10. If so force disable HPET as that
* stops counting in PC10. This check is overbroad as it does not take any
* of the following into account:
*
* - ACPI tables
* - Enablement of intel_idle
* - Command line arguments which limit intel_idle C-state support
*
* That's perfectly fine. HPET is a piece of hardware designed by committee
* and the only reasons why it is still in use on modern systems is the
* fact that it is impossible to reliably query TSC and CPU frequency via
* CPUID or firmware.
*
* If HPET is functional it is useful for calibrating TSC, but this can be
* done via PMTIMER as well which seems to be the last remaining timer on
* X86/INTEL platforms that has not been completely wreckaged by feature
* creep.
*
* In theory HPET support should be removed altogether, but there are older
* systems out there which depend on it because TSC and APIC timer are
* dysfunctional in deeper C-states.
*
* It's only 20 years now that hardware people have been asked to provide
* reliable and discoverable facilities which can be used for timekeeping
* and per CPU timer interrupts.
*
* The probability that this problem is going to be solved in the
* forseeable future is close to zero, so the kernel has to be cluttered
* with heuristics to keep up with the ever growing amount of hardware and
* firmware trainwrecks. Hopefully some day hardware people will understand
* that the approach of "This can be fixed in software" is not sustainable.
* Hope dies last...
*/
static bool __init hpet_is_pc10_damaged(void)
{
unsigned long long pcfg;
/* Check whether PC10 substates are supported */
if (!mwait_pc10_supported())
return false;
/* Check whether PC10 is enabled in PKG C-state limit */
rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, pcfg);
if ((pcfg & 0xF) < 8)
return false;
if (hpet_force_user) {
pr_warn("HPET force enabled via command line, but dysfunctional in PC10.\n");
return false;
}
pr_info("HPET dysfunctional in PC10. Force disabled.\n");
boot_hpet_disable = true;
return true;
}
/**
* hpet_enable - Try to setup the HPET timer. Returns 1 on success.
*/
int __init hpet_enable(void)
{
u32 hpet_period, cfg, id, irq;
unsigned int i, channels;
struct hpet_channel *hc;
u64 freq;
if (!is_hpet_capable())
return 0;
if (hpet_is_pc10_damaged())
return 0;
hpet_set_mapping();
if (!hpet_virt_address)
return 0;
/* Validate that the config register is working */
if (!hpet_cfg_working())
goto out_nohpet;
/*
* Read the period and check for a sane value:
*/
hpet_period = hpet_readl(HPET_PERIOD);
if (hpet_period < HPET_MIN_PERIOD || hpet_period > HPET_MAX_PERIOD)
goto out_nohpet;
/* The period is a femtoseconds value. Convert it to a frequency. */
freq = FSEC_PER_SEC;
do_div(freq, hpet_period);
hpet_freq = freq;
/*
* Read the HPET ID register to retrieve the IRQ routing
* information and the number of channels
*/
id = hpet_readl(HPET_ID);
hpet_print_config();
/* This is the HPET channel number which is zero based */
channels = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT) + 1;
/*
* The legacy routing mode needs at least two channels, tick timer
* and the rtc emulation channel.
*/
if (IS_ENABLED(CONFIG_HPET_EMULATE_RTC) && channels < 2)
goto out_nohpet;
hc = kcalloc(channels, sizeof(*hc), GFP_KERNEL);
if (!hc) {
pr_warn("Disabling HPET.\n");
goto out_nohpet;
}
hpet_base.channels = hc;
hpet_base.nr_channels = channels;
/* Read, store and sanitize the global configuration */
cfg = hpet_readl(HPET_CFG);
hpet_base.boot_cfg = cfg;
cfg &= ~(HPET_CFG_ENABLE | HPET_CFG_LEGACY);
hpet_writel(cfg, HPET_CFG);
if (cfg)
pr_warn("Global config: Unknown bits %#x\n", cfg);
/* Read, store and sanitize the per channel configuration */
for (i = 0; i < channels; i++, hc++) {
hc->num = i;
cfg = hpet_readl(HPET_Tn_CFG(i));
hc->boot_cfg = cfg;
irq = (cfg & Tn_INT_ROUTE_CNF_MASK) >> Tn_INT_ROUTE_CNF_SHIFT;
hc->irq = irq;
cfg &= ~(HPET_TN_ENABLE | HPET_TN_LEVEL | HPET_TN_FSB);
hpet_writel(cfg, HPET_Tn_CFG(i));
cfg &= ~(HPET_TN_PERIODIC | HPET_TN_PERIODIC_CAP
| HPET_TN_64BIT_CAP | HPET_TN_32BIT | HPET_TN_ROUTE
| HPET_TN_FSB | HPET_TN_FSB_CAP);
if (cfg)
pr_warn("Channel #%u config: Unknown bits %#x\n", i, cfg);
}
hpet_print_config();
/*
* Validate that the counter is counting. This needs to be done
* after sanitizing the config registers to properly deal with
* force enabled HPETs.
*/
if (!hpet_counting())
goto out_nohpet;
if (tsc_clocksource_watchdog_disabled())
clocksource_hpet.flags |= CLOCK_SOURCE_MUST_VERIFY;
clocksource_register_hz(&clocksource_hpet, (u32)hpet_freq);
if (id & HPET_ID_LEGSUP) {
hpet_legacy_clockevent_register(&hpet_base.channels[0]);
hpet_base.channels[0].mode = HPET_MODE_LEGACY;
if (IS_ENABLED(CONFIG_HPET_EMULATE_RTC))
hpet_base.channels[1].mode = HPET_MODE_LEGACY;
return 1;
}
return 0;
out_nohpet:
kfree(hpet_base.channels);
hpet_base.channels = NULL;
hpet_base.nr_channels = 0;
hpet_clear_mapping();
hpet_address = 0;
return 0;
}
/*
* The late initialization runs after the PCI quirks have been invoked
* which might have detected a system on which the HPET can be enforced.
*
* Also, the MSI machinery is not working yet when the HPET is initialized
* early.
*
* If the HPET is enabled, then:
*
* 1) Reserve one channel for /dev/hpet if CONFIG_HPET=y
* 2) Reserve up to num_possible_cpus() channels as per CPU clockevents
* 3) Setup /dev/hpet if CONFIG_HPET=y
* 4) Register hotplug callbacks when clockevents are available
*/
static __init int hpet_late_init(void)
{
int ret;
if (!hpet_address) {
if (!force_hpet_address)
return -ENODEV;
hpet_address = force_hpet_address;
hpet_enable();
}
if (!hpet_virt_address)
return -ENODEV;
hpet_select_device_channel();
hpet_select_clockevents();
hpet_reserve_platform_timers();
hpet_print_config();
if (!hpet_base.nr_clockevents)
return 0;
ret = cpuhp_setup_state(CPUHP_AP_X86_HPET_ONLINE, "x86/hpet:online",
hpet_cpuhp_online, NULL);
if (ret)
return ret;
ret = cpuhp_setup_state(CPUHP_X86_HPET_DEAD, "x86/hpet:dead", NULL,
hpet_cpuhp_dead);
if (ret)
goto err_cpuhp;
return 0;
err_cpuhp:
cpuhp_remove_state(CPUHP_AP_X86_HPET_ONLINE);
return ret;
}
fs_initcall(hpet_late_init);
void hpet_disable(void)
{
unsigned int i;
u32 cfg;
if (!is_hpet_capable() || !hpet_virt_address)
return;
/* Restore boot configuration with the enable bit cleared */
cfg = hpet_base.boot_cfg;
cfg &= ~HPET_CFG_ENABLE;
hpet_writel(cfg, HPET_CFG);
/* Restore the channel boot configuration */
for (i = 0; i < hpet_base.nr_channels; i++)
hpet_writel(hpet_base.channels[i].boot_cfg, HPET_Tn_CFG(i));
/* If the HPET was enabled at boot time, reenable it */
if (hpet_base.boot_cfg & HPET_CFG_ENABLE)
hpet_writel(hpet_base.boot_cfg, HPET_CFG);
}
#ifdef CONFIG_HPET_EMULATE_RTC
/*
* HPET in LegacyReplacement mode eats up the RTC interrupt line. When HPET
* is enabled, we support RTC interrupt functionality in software.
*
* RTC has 3 kinds of interrupts:
*
* 1) Update Interrupt - generate an interrupt, every second, when the
* RTC clock is updated
* 2) Alarm Interrupt - generate an interrupt at a specific time of day
* 3) Periodic Interrupt - generate periodic interrupt, with frequencies
* 2Hz-8192Hz (2Hz-64Hz for non-root user) (all frequencies in powers of 2)
*
* (1) and (2) above are implemented using polling at a frequency of 64 Hz:
* DEFAULT_RTC_INT_FREQ.
*
* The exact frequency is a tradeoff between accuracy and interrupt overhead.
*
* For (3), we use interrupts at 64 Hz, or the user specified periodic frequency,
* if it's higher.
*/
#include <linux/mc146818rtc.h>
#include <linux/rtc.h>
#define DEFAULT_RTC_INT_FREQ 64
#define DEFAULT_RTC_SHIFT 6
#define RTC_NUM_INTS 1
static unsigned long hpet_rtc_flags;
static int hpet_prev_update_sec;
static struct rtc_time hpet_alarm_time;
static unsigned long hpet_pie_count;
static u32 hpet_t1_cmp;
static u32 hpet_default_delta;
static u32 hpet_pie_delta;
static unsigned long hpet_pie_limit;
static rtc_irq_handler irq_handler;
/*
* Check that the HPET counter c1 is ahead of c2
*/
static inline int hpet_cnt_ahead(u32 c1, u32 c2)
{
return (s32)(c2 - c1) < 0;
}
/*
* Registers a IRQ handler.
*/
int hpet_register_irq_handler(rtc_irq_handler handler)
{
if (!is_hpet_enabled())
return -ENODEV;
if (irq_handler)
return -EBUSY;
irq_handler = handler;
return 0;
}
EXPORT_SYMBOL_GPL(hpet_register_irq_handler);
/*
* Deregisters the IRQ handler registered with hpet_register_irq_handler()
* and does cleanup.
*/
void hpet_unregister_irq_handler(rtc_irq_handler handler)
{
if (!is_hpet_enabled())
return;
irq_handler = NULL;
hpet_rtc_flags = 0;
}
EXPORT_SYMBOL_GPL(hpet_unregister_irq_handler);
/*
* Channel 1 for RTC emulation. We use one shot mode, as periodic mode
* is not supported by all HPET implementations for channel 1.
*
* hpet_rtc_timer_init() is called when the rtc is initialized.
*/
int hpet_rtc_timer_init(void)
{
unsigned int cfg, cnt, delta;
unsigned long flags;
if (!is_hpet_enabled())
return 0;
if (!hpet_default_delta) {
struct clock_event_device *evt = &hpet_base.channels[0].evt;
uint64_t clc;
clc = (uint64_t) evt->mult * NSEC_PER_SEC;
clc >>= evt->shift + DEFAULT_RTC_SHIFT;
hpet_default_delta = clc;
}
if (!(hpet_rtc_flags & RTC_PIE) || hpet_pie_limit)
delta = hpet_default_delta;
else
delta = hpet_pie_delta;
local_irq_save(flags);
cnt = delta + hpet_readl(HPET_COUNTER);
hpet_writel(cnt, HPET_T1_CMP);
hpet_t1_cmp = cnt;
cfg = hpet_readl(HPET_T1_CFG);
cfg &= ~HPET_TN_PERIODIC;
cfg |= HPET_TN_ENABLE | HPET_TN_32BIT;
hpet_writel(cfg, HPET_T1_CFG);
local_irq_restore(flags);
return 1;
}
EXPORT_SYMBOL_GPL(hpet_rtc_timer_init);
static void hpet_disable_rtc_channel(void)
{
u32 cfg = hpet_readl(HPET_T1_CFG);
cfg &= ~HPET_TN_ENABLE;
hpet_writel(cfg, HPET_T1_CFG);
}
/*
* The functions below are called from rtc driver.
* Return 0 if HPET is not being used.
* Otherwise do the necessary changes and return 1.
*/
int hpet_mask_rtc_irq_bit(unsigned long bit_mask)
{
if (!is_hpet_enabled())
return 0;
hpet_rtc_flags &= ~bit_mask;
if (unlikely(!hpet_rtc_flags))
hpet_disable_rtc_channel();
return 1;
}
EXPORT_SYMBOL_GPL(hpet_mask_rtc_irq_bit);
int hpet_set_rtc_irq_bit(unsigned long bit_mask)
{
unsigned long oldbits = hpet_rtc_flags;
if (!is_hpet_enabled())
return 0;
hpet_rtc_flags |= bit_mask;
if ((bit_mask & RTC_UIE) && !(oldbits & RTC_UIE))
hpet_prev_update_sec = -1;
if (!oldbits)
hpet_rtc_timer_init();
return 1;
}
EXPORT_SYMBOL_GPL(hpet_set_rtc_irq_bit);
int hpet_set_alarm_time(unsigned char hrs, unsigned char min, unsigned char sec)
{
if (!is_hpet_enabled())
return 0;
hpet_alarm_time.tm_hour = hrs;
hpet_alarm_time.tm_min = min;
hpet_alarm_time.tm_sec = sec;
return 1;
}
EXPORT_SYMBOL_GPL(hpet_set_alarm_time);
int hpet_set_periodic_freq(unsigned long freq)
{
uint64_t clc;
if (!is_hpet_enabled())
return 0;
if (freq <= DEFAULT_RTC_INT_FREQ) {
hpet_pie_limit = DEFAULT_RTC_INT_FREQ / freq;
} else {
struct clock_event_device *evt = &hpet_base.channels[0].evt;
clc = (uint64_t) evt->mult * NSEC_PER_SEC;
do_div(clc, freq);
clc >>= evt->shift;
hpet_pie_delta = clc;
hpet_pie_limit = 0;
}
return 1;
}
EXPORT_SYMBOL_GPL(hpet_set_periodic_freq);
int hpet_rtc_dropped_irq(void)
{
return is_hpet_enabled();
}
EXPORT_SYMBOL_GPL(hpet_rtc_dropped_irq);
static void hpet_rtc_timer_reinit(void)
{
unsigned int delta;
int lost_ints = -1;
if (unlikely(!hpet_rtc_flags))
hpet_disable_rtc_channel();
if (!(hpet_rtc_flags & RTC_PIE) || hpet_pie_limit)
delta = hpet_default_delta;
else
delta = hpet_pie_delta;
/*
* Increment the comparator value until we are ahead of the
* current count.
*/
do {
hpet_t1_cmp += delta;
hpet_writel(hpet_t1_cmp, HPET_T1_CMP);
lost_ints++;
} while (!hpet_cnt_ahead(hpet_t1_cmp, hpet_readl(HPET_COUNTER)));
if (lost_ints) {
if (hpet_rtc_flags & RTC_PIE)
hpet_pie_count += lost_ints;
if (printk_ratelimit())
pr_warn("Lost %d RTC interrupts\n", lost_ints);
}
}
irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
{
struct rtc_time curr_time;
unsigned long rtc_int_flag = 0;
hpet_rtc_timer_reinit();
memset(&curr_time, 0, sizeof(struct rtc_time));
if (hpet_rtc_flags & (RTC_UIE | RTC_AIE)) {
if (unlikely(mc146818_get_time(&curr_time) < 0)) {
pr_err_ratelimited("unable to read current time from RTC\n");
return IRQ_HANDLED;
}
}
if (hpet_rtc_flags & RTC_UIE &&
curr_time.tm_sec != hpet_prev_update_sec) {
if (hpet_prev_update_sec >= 0)
rtc_int_flag = RTC_UF;
hpet_prev_update_sec = curr_time.tm_sec;
}
if (hpet_rtc_flags & RTC_PIE && ++hpet_pie_count >= hpet_pie_limit) {
rtc_int_flag |= RTC_PF;
hpet_pie_count = 0;
}
if (hpet_rtc_flags & RTC_AIE &&
(curr_time.tm_sec == hpet_alarm_time.tm_sec) &&
(curr_time.tm_min == hpet_alarm_time.tm_min) &&
(curr_time.tm_hour == hpet_alarm_time.tm_hour))
rtc_int_flag |= RTC_AF;
if (rtc_int_flag) {
rtc_int_flag |= (RTC_IRQF | (RTC_NUM_INTS << 8));
if (irq_handler)
irq_handler(rtc_int_flag, dev_id);
}
return IRQ_HANDLED;
}
EXPORT_SYMBOL_GPL(hpet_rtc_interrupt);
#endif